The present invention relates to a method and an apparatus for repairing the damaged surface of the refractory lining which comprises measuring the surface of the lining of the refractory lined vessel in a hot atmosphere and repairing the damaged surface of the refractory lining on the basis of the results of the measurement.
The refractory lined vessels referred to in this invention are ladles, torpedo cars, mixers, converters, electric furnaces, spare or additional refining furnaces, and the like which are used in the steel making.
These vessels are, as shown in FIG. 1, constructed in such a manner that the outer shell has a metal frame 1, and the inner peripheral surface is formed with a permanent lining 2 and a wear lining 3. The lining refractories to be used for the linings 2 and 3 are made of refractory mix or monolithic refractories.
The above-mentioned permanent lining 2 is also called the safety lining and, in the normal operation, is not exposed as the working surface and is not worn out.
Unlike to this permanent lining 2, the wear lining 3 is subjected to abrasion due to hot metal or molten steel together with corrosion caused by the reaction with the slag in the steel making operation, or erosion due to spalling, and is gradually worn out. When it reaches the condition as in the drawings by dotted line 3, the operation is stopped. The wear condition of the wear lining 3 varies depending on the kind of vessel, and operating conditions.
After the suspension of the operation, the vessel is sufficiently cleaned, and the remaining wear lining 3 is demolished and the new wear lining 3 is applied to complete the repair. The period from one repair until the next, i.e., the operating period greatly varies depending on whether or not an intermediate repair has been made. Generally, for example, with respect to the ladle, this period is 70 - 150 times; with the the torpedo car, it is 700 - 1500 times; and, with the converter, it is 500 - 1500 times.
The repair process varies with respect to the contents depending on the kind of vessel, but generally, the repair process is as follows: cooling .fwdarw. demolition of the remaining wear lining .fwdarw. new building of the wear lining. This vessel repair process will be explained by taking the converter (capacity 100 t) as an example which takes a relatively short work period. The cooling time is 50 - 60 hours, the demolition time of the remaining wear lining; 10 - 15 hours; the building of the new wear lining, 60 - 70 hours; and, miscellaneous work, 10 - 20 hours, with a total of 130 - 160 hours being required.
Also, prior to the operation of the vessel, after the repair of the furnace, the drying and temperature elevating operations are carried out, and therefore more time is required.
As explained in the foregoing, for the repair of the refractory lined vessel, it is inevitable that there will be a long unproductive period of time.
With a view to shortening the unproductive time and reduce the consumption of the refractory, gunning has lately been adopted as the repair technique in the hot atmosphere. This gunning repair method is mainly to repair the local damaged portion in the hot atmosphere, and refractory materials are normally used which are almost equal to or of a slightly higher class than said refractory.
With this repair, the local damaged portion which is considered to be the direct cause of the furnace repair is repaired, and the service life is extended. Moreover, the damage balance of the lining refractory is maintained, whereby the consumption of the refractory can be reduced.
However, this gunning repair has had problems in the following points.
Namely, in the repair method, the damaged portions are discovered by the visual (naked eye) observation of the operator. As a result, the damaged portions, other than those remakably damaged, tend to be overlooked in many cases. Thus, when the whole lining is damaged, it becomes difficult to make a comparison of the damaged portion of the lining with the reference lining surface, and the amount of damage cannot be grasped wholly. Therefore, the repair is forestalled, and also, materials beyond the necessity tend to be used which are the drawbacks of the gunning repair method.
Also, because repair is started from the time when the local damage has advanced too far, the yield of the repair materials becomes favorable but it is difficult to extend the service life greatly.
Also, since the gunning repair is performed at the operation time of the vessel, it is preferable to perform it in as short a time as possible so that it does not pose an obstacle to production. But, in the practical pattern of inspection of the inside of the furnace by visual observation, it is difficult to improve the accuracy of the repair.
As described in the foregoing, the conventional repair method of the lining refractory of the vessel was involved with the problems in the gunning repair which was partly used in case of the full surface repair of the ordinary lining refractory and also in the consumption of the refractory and the nonoperation time on account of the repair.